msm: kgsl: Check the validity of gpuaddr

In kgsl_mmu_gpuaddr_in_range(), actually check if the gpuaddr is
within the requisite bounds instead of directly returning success.
In addition, change check for the special SVM case to check
specifically if cpu map is enabled.

Change-Id: Ib3a313231bcc191fefffd487d473ffc3e9fa53d8
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>